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Atmospheric polarisation measured by POLDER. Polarisation: Stokes vectors, direction, etc. POLDER Results of analysis of POLDER polarisation data Conclusion / Relevance to SCIAMACHY. 28 August, 2003. Atmospheric light: Stokes vector {I, Q, U, V}. Polarisation.
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Atmospheric polarisation measured by POLDER • Polarisation: Stokes vectors, direction, etc. • POLDER • Results of analysis of POLDER polarisation data • Conclusion / Relevance to SCIAMACHY 28 August, 2003
Atmospheric light: Stokes vector {I, Q, U, V} Polarisation V = 0 ; Q and U describe the linear part of polarisation • Q = I0°– I90° • U = I45°– I135° • Q = P I cos 2 • U = P I sin 2 • P = degree of polarisation • = direction of polarisation
POLDER (ADEOS-I) • CCD detector matrix. • Bandfilter carousel. • Resolution 6 x 7 km2. • Polarisation at 443, 670 and 865 nm. • I, Q, and U.
Comparison between POLDER and single scattering theory: Direction of polarisation = ½ atan U/Q
Conclusions • Spread for a large part determined by measurement errors in POLDER data, especially at larger wavelengths. • Direction of polarisation ~ single scattering value. • No need to measure it (SCIAMACHY). • It’s BETTER not to use a measured value (SCIAMACHY).